This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Receptor-ligand interactions and the induction of signal transduction biochemistry are the driving force for all regulatory events in cell biology. This regulation is especially evident in the immune system, which exhibits numerous receptor-ligand interactions that promote immune cell differentiation, proliferation, apoptosis, and activation of effector functions. Accordingly, signal transduction biochemistry is central to understanding the biological events within immune cell homeostasis. The body of knowledge of immune cell signaling has matured considerably over the past ten years, especially with the discovery of the central role for tyrosine protein kinases in regulatory protein-protein interactions. Since it is a nascent field, the techniques used to study signaling events induced by cytokines or other immune cell activators are fairly specialized and perhaps not readily acquired by inexperienced laboratories without direct support. Given the similarity of assays that apply from one receptor to another, we expect benefit from past experience for those who study related signaling systems. Thus, this application proposes to continue to support a core facility to house expertise and equipment that focuses on immune cell signal transduction biochemistry. It will be used as a knowledge-base and technical resource for new investigators who find a need to explore signaling events in various immune responses, and will facilitate development and transfer of expertise and specific assays to researchers studying other signaling networks.